Mobile wireless communications device having buffered clock distribution network for microprocessor and RF circuits

ABSTRACT

A mobile wireless communications device includes a circuit board carried by a housing. A microprocessor, RF transceiver and circuitry are carried by the circuit board and operative with each other. Clock buffer circuitry is carried by the circuit board and connected to the RF transceiver and circuitry and microprocessor for isolating a clock signal from the noise of the microprocessor and allowing greater isolation for the RF transceiver from RF circuitry.

FIELD OF THE INVENTION

The present invention relates to the field of communications device, andmore particularly, this invention relates to mobile wirelesscommunications devices and related methods.

BACKGROUND OF THE INVENTION

Mobile wireless communications devices, such as cellular telephones andsimilar communications devices, include a housing and circuit boardcarried by the housing. A microprocessor, radio frequency (RF)transceiver and RF circuitry can be carried by the circuit board andoperative with each other. An antenna could be located external orwithin the housing. A clock, such as a crystal oscillator, could bepositioned external to the components and off the circuit board ormounted on the circuit board, and provide a clocking signal to themicroprocessor, RF transceiver and other RF circuitry, including anyBluetooth modules, phase locked loop circuits, and local oscillator (LO)circuits. Typically, spurious signals and jitters caused by digitalnoise from a microprocessor creates problems because it shares the sameclock with the RF circuits, such as the reference clock input to thephase locked loop. The clock from the crystal oscillator provides thereference clock input signal to both the RF circuits, such as the phasedlocked loop circuit, RF circuits and digital circuits, such as themicroprocessor, but without buffering.

The microprocessor generates many digital noises that find their wayback from the clock reference input of the microprocessor to thereference clock lines with which the RF circuits are sharing. Thesedigital noises are conductively coupled to the RF circuits, includingany RF transceiver, Bluetooth module and other RF circuits, such as alocal oscillator and phase locked loop circuits, to cause spurioussignals and jitters in the circuits, which in turn, degrade the RFperformance or cause a radio to fail certain specifications.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is a schematic block diagram of an example of a mobile wirelesscommunications device figured as a handheld device and illustratingbasic internal components thereof such as can be used in onenon-limiting embodiment.

FIG. 2 is a front elevation view of the mobile wireless communicationsdevice of FIG. 1.

FIG. 3 is a schematic block diagram showing basic functional circuitcomponents that can be used in the mobile wireless communications deviceof FIGS. 1 and 2.

FIG. 4 is a schematic block diagram showing basic components of a radiotransceiver and other RF circuits such as a Bluetooth module, and phaselocked loop circuit operative with the microprocessor and showing theclock buffer circuitry.

FIGS. 5A-5C are interrelated schematic circuit diagrams showing amicroprocessor (FIG. 5B) connected to clock buffer circuitry, such asshown in FIG. 5C.

FIG. 6 is a block diagram of a typical Bluetooth module that can be usedwith the mobile wireless communications device shown in FIGS. 1-4 and5A-5C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Different embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsare shown. Many different forms can be set forth and describedembodiments should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope to those skilled in the art. Like numbers refer to like elementsthroughout, and prime notation is used to indicate similar elements inalternative embodiments.

A mobile wireless communications device includes a housing and a circuitboard carried by the housing. A microprocessor, a radio frequency (RF)transceiver and RF circuitry are carried by the circuit board andoperative with each other. Clock buffer circuitry is carried by thecircuit board and connected to the RF transceiver, RF circuitry andmicroprocessor for isolating a clock signal from the noise of themicroprocessor and allowing greater isolation for the RF transceiverfrom RF circuitry.

In accordance with one non-limiting embodiment, the RF circuitryincludes a Bluetooth module and the clock buffer circuitry is connectedto the Bluetooth module for isolating a clock signal after the RFtransceiver. The RF circuitry could also include a phase locked loopcircuit and the clock buffer circuitry is connected to the phase lockedlooped circuit for isolating a clock signal after the RF transceiver andBluetooth module.

In yet another non-limiting example, the RF transceiver is formed as aGSM/GPRS (Global System for Mobile communications/General Packet RadioService) system. The clock buffer circuitry could be formed as aplurality of serially connected buffers each having an output connectedto a predetermined one of the RF circuitry and microprocessor. Eachbuffer could provide about 40 to about 80 decibels of reversed isolationfrom its output to its input in a non-limiting example. The plurality ofserially connected buffers could also be formed as transistors connectedas emitter followers. The housing can be configured for handheldoperation and the RF transceiver, RF circuitry and microprocessor can beoperative as a cellular communications device. An antenna could becarried by the housing and operative with the RF transceiver.

In various embodiments, the clock buffer circuitry is formed as acascaded clock buffer circuit and reduces digital noise as spuriousjitters from a microprocessor that shares the same clock with various RFcircuits, such as a reference clock input to phased locked loops. Aclock signal can be generated from a crystal oscillator and provide areference clock input signal to RF circuits, such as a phased lockedloop and other digital circuits, for example, the microprocessor.Because the microprocessor generates digital noises that pass from theclock reference input of the microprocessor to the reference clock lineswith which the RF circuits are sharing, these digital noises can beconductively coupled to the RF circuits and cause spurious signals andjitters in the local oscillator circuits, which degrade the RFperformance and cause the radio to fail certain specifications.

Different embodiments show that different clock signals can be isolatedfrom the noise of the microprocessor. More sensitive RF circuits, forexample, the GSM/GPRS chip set, could be connected to the crystaloscillator output first with proper impedance matching. The output of afirst buffer circuit could be connected to a less sensitive RF circuit,for example, a Bluetooth module or chip. The buffer circuit couldprovide about 40 to about 80 decibel reversed isolation from its outputto the input. Other buffer circuits could be included with separateisolation.

A brief description will now proceed relative to FIGS. 1-3, whichdisclose an example of a mobile wireless communications device, forexample, a handheld portable cellular radio, which can incorporate thenon-limiting examples of the various buffering circuits and clockdistribution network. FIGS. 1-3 are representative non-limiting examplesof the many different types of functional circuit components and theirinterconnection, and operative for use with the clock distributionnetwork and buffering circuits as described.

Referring initially to FIGS. 1 and 2, an example of a mobile wirelesscommunications device 20, such as a handheld portable cellular radio,which can be used with the present invention is first described. Thisdevice 20 illustratively includes a housing 21 having an upper portion46 and a lower portion 47, and a dielectric substrate (i.e., circuitboard) 67, such as a conventional printed circuit board (PCB) substrate,for example, carried by the housing. A housing cover (not shown indetail) would typically cover the front portion of the housing. The termcircuit board 67 as used hereinafter can refer to any dielectricsubstrate, PCB, ceramic substrate or other circuit carrying structurefor carrying signal circuits and electronic components within the mobilewireless communications device 20. The illustrated housing 21 is astatic housing, for example, as opposed to a flip or sliding housingwhich are used in many cellular telephones. However, these and otherhousing configurations may also be used.

Circuitry 48 is carried by the circuit board 67, such as amicroprocessor, memory, one or more wireless transceivers (e.g.,cellular, WLAN, etc.), which includes RF circuitry, including audio andpower circuitry, including any keyboard circuitry. It should beunderstood that keyboard circuitry could be on a separate keyboard,etc., as will be appreciated by those skilled in the art. A battery (notshown) is also preferably carried by the housing 21 for supplying powerto the circuitry 48. The term RF circuitry could encompass theinteroperable RF transceiver circuitry, power circuitry and audiocircuitry.

Furthermore, an audio output transducer 49 (e.g., a speaker) is carriedby an upper portion 46 of the housing 21 and connected to the circuitry48. One or more user input interface devices, such as a keypad(keyboard) 23 (FIG. 2), is also preferably carried by the housing 21 andconnected to the circuitry 48. The term keypad as used herein alsorefers to the term keyboard, indicating the user input devices havinglettered and/or numbered keys commonly known and other embodiments,including multi-top or predictive entry modes. Other examples of userinput interface devices include a scroll wheel 37 and a back button 36.Of course, it will be appreciated that other user input interfacedevices (e.g., a stylus or touch screen interface) may be used in otherembodiments.

An antenna 45 is preferably positioned at the lower portion 47 in thehousing and can be formed as a pattern of conductive traces that make anantenna circuit, which physically forms the antenna. It is connected tothe circuitry 48 on the main circuit board 67. In one non-limitingexample, the antenna could be formed on an antenna circuit board sectionthat extends from the circuit board at the lower portion of the housing.By placing the antenna 45 adjacent the lower portion 47 of the housing21, the distance is advantageously increased between the antenna and theuser's head when the phone is in use to aid in complying with applicableSAR requirements. Also, a separate keyboard circuit board could be used.

More particularly, a user will typically hold the upper portion of thehousing 21 very close to his head so that the audio output transducer 49is directly next to his ear. Yet, the lower portion 47 of the housing 21where an audio input transducer (i.e., microphone) is located need notbe placed directly next to a user's mouth, and can be held away from theuser's mouth. That is, holding the audio input transducer close to theuser's mouth may not only be uncomfortable for the user, but it may alsodistort the user's voice in some circumstances. In addition, theplacement of the antenna 45 adjacent the lower portion 47 of the housing21 also advantageously spaces the antenna farther away from the user'sbrain.

Another important benefit of placing the antenna 45 adjacent the lowerportion 47 of the housing 21 is that this may allow for less impact onantenna performance due to blockage by a user's hand. That is, userstypically hold cellular phones toward the middle to upper portion of thephone housing, and are therefore more likely to put their hands oversuch an antenna than they are an antenna mounted adjacent the lowerportion 47 of the housing 21. Accordingly, more reliable performance maybe achieved from placing the antenna 45 adjacent the lower portion 47 ofthe housing 21.

Still another benefit of this configuration is that it provides moreroom for one or more auxiliary input/output (I/O) devices 50 to becarried at the upper portion 46 of the housing. Furthermore, byseparating the antenna 45 from the auxiliary I/O device(s) 50, this mayallow for reduced interference therebetween.

Some examples of auxiliary I/O devices 50 include a WLAN (e.g.,Bluetooth, IEEE 802.11) antenna for providing WLAN communicationcapabilities, and/or a satellite positioning system (e.g., GPS, Galileo,etc.) antenna for providing position location capabilities, as will beappreciated by those skilled in the art. Other examples of auxiliary I/Odevices 50 include a second audio output transducer (e.g., a speaker forspeaker phone operation), and a camera lens for providing digital cameracapabilities, an electrical device connector (e.g., USB, headphone,secure digital (SD) or memory card, etc.).

It should be noted that the term “input/output” as used herein for theauxiliary I/O device(s) 50 means that such devices may have input and/oroutput capabilities, and they need not provide both in all embodiments.That is, devices such as camera lenses may only receive an opticalinput, for example, while a headphone jack may only provide an audiooutput.

The device 20 further illustratively includes a display 22, for example,a liquid crystal display (LCD) carried by the housing 21 and connectedto the circuitry 48. A back button 36 and scroll wheel 37 can also beconnected to the circuitry 48 for allowing a user to navigate menus,text, etc., as will be appreciated by those skilled in the art. Thescroll wheel 37 may also be referred to as a “thumb wheel” or a “trackwheel” in some instances. The keypad 23 illustratively includes aplurality of multi-symbol keys 24 each having indicia of a plurality ofrespective symbols thereon. The keypad 23 also illustratively includesan alternate function key 25, a next key 26, a space key 27, a shift key28, a return (or enter) key 29, and a backspace/delete key 30.

The next key 26 is also used to enter a “*” symbol upon first pressingor actuating the alternate function key 25. Similarly, the space key 27,shift key 28 and backspace key 30 are used to enter a “0” and “#”,respectively, upon first actuating the alternate function key 25. Thekeypad 23 further illustratively includes a send key 31, an end key 32,and a convenience (i.e., menu) key 39 for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.

Moreover, the symbols on each key 24 are arranged in top and bottomrows. The symbols in the bottom rows are entered when a user presses akey 24 without first pressing the alternate function key 25, while thetop row symbols are entered by first pressing the alternate functionkey. As seen in FIG. 2, the multi-symbol keys 24 are arranged in thefirst three rows on the keypad 23 below the send and end keys 31, 32.Furthermore, the letter symbols on each of the keys 24 are arranged todefine a QWERTY layout. That is, the letters on the keypad 23 arepresented in a three-row format, with the letters of each row being inthe same order and relative position as in a standard QWERTY keypad.

Each row of keys (including the fourth row of function keys 25-29) isarranged in five columns. The multi-symbol keys 24 in the second, third,and fourth columns of the first, second, and third rows have numericindicia thereon (i.e., 1 through 9) accessible by first actuating thealternate function key 25. Coupled with the next, space, and shift keys26, 27, 28, which respectively enter a “*”, “0”, and “#” upon firstactuating the alternate function key 25, as noted above, this set ofkeys defines a standard telephone keypad layout, as would be found on atraditional touch-tone telephone, as will be appreciated by thoseskilled in the art.

Accordingly, the mobile wireless communications device 20 as describedmay advantageously be used not only as a traditional cellular phone, butit may also be conveniently used for sending and/or receiving data overa cellular or other network, such as Internet and email data, forexample. Of course, other keypad configurations may also be used inother embodiments. Multi-tap or predictive entry modes may be used fortyping e-mails, etc. as will be appreciated by those skilled in the art.

The antenna 45 is preferably formed as a multi-frequency band antenna,which provides enhanced transmission and reception characteristics overmultiple operating frequencies. More particularly, the antenna 45 isdesigned to provide high gain, desired impedance matching, and meetapplicable SAR requirements over a relatively wide bandwidth andmultiple cellular frequency bands. By way of example, the antenna 45preferably operates over five bands, namely a 850 MHz Global System forMobile Communications (GSM) band, a 900 MHz GSM band, a DCS band, a PCSband, and a WCDMA band (i.e., up to about 2100 MHz), although it may beused for other bands/frequencies as well. To conserve space, the antenna45 may advantageously be implemented in three dimensions although it maybe implemented in two-dimensional or planar embodiments as well.

The mobile wireless communications device shown in FIGS. 1 and 2 canincorporate e-mail and messaging accounts and provide differentfunctions such as composing e-mail, PIN messages, and SMS messages. Thedevice can manage messages through an appropriate menu that can beretrieved by choosing a messages icon. An address book function couldadd contacts, allow management of an address book, set address bookoptions and manage SIM card phone books. A phone menu could allow forthe making and answering of phone calls using different phone features,managing phone call logs, setting phone options, and viewing phoneinformation. A browser application could permit the browsing of webpages, configuring a browser, adding bookmarks, and changing browseroptions. Other applications could include a task, memo pad, calculator,alarm and games, as well as handheld options with various references.

A calendar icon can be chosen for entering a calendar program that canbe used for establishing and managing events such as meetings orappointments. The calendar program could be any type of messaging orappointment/meeting program that allows an organizer to establish anevent, for example, an appointment or meeting.

A non-limiting example of various functional components that can be usedin the exemplary mobile wireless communications device 20 of FIGS. 1 and2 is further described in the example below with reference to FIG. 3.The device 20 illustratively includes a housing 120, a keypad 140 and anoutput device 160. The output device 160 shown is preferably a display,which is preferably a full graphic LCD. Other types of output devicesmay alternatively be used. A processing device 180 is contained withinthe housing 120 and is coupled between the keypad 140 and the display160. The processing device 180 controls the operation of the display160, as well as the overall operation of the mobile device 20, inresponse to actuation of keys on the keypad 140 by the user.

The housing 120 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 180, other parts of the mobiledevice 20 are shown schematically in FIG. 3. These include acommunications subsystem 101; a short-range communications subsystem102; the keypad 140 and the display 160, along with other input/outputdevices 106, 108, 110 and 112; as well as memory devices 116, 118 andvarious other device subsystems 121. The mobile device 20 is preferablya two-way RF communications device having voice and data communicationscapabilities. In addition, the mobile device 20 preferably has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the processing device 180 ispreferably stored in a persistent store, such as the flash memory 116,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)118. Communications signals received by the mobile device may also bestored in the RAM 118.

The processing device 180, in addition to its operating systemfunctions, enables execution of software applications 130A-130N on thedevice 20. A predetermined set of applications that control basic deviceoperations, such as data and voice communications 130A and 130B, may beinstalled on the device 20 during manufacture. In addition, a personalinformation manager (PIM) application may be installed duringmanufacture. The PIM is preferably capable of organizing and managingdata items, such as e-mail, calendar events, voice mails, appointments,and task items. The PIM application is also preferably capable ofsending and receiving data items via a wireless network 141. Preferably,the PIM data items are seamlessly integrated, synchronized and updatedvia the wireless network 141 with the device user's corresponding dataitems stored or associated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 101, and possibly throughthe short-range communications subsystem. The communications subsystem101 includes a receiver 150, a transmitter 152, and one or more antennae154 and 156. In addition, the communications subsystem 101 also includesa processing module, such as a digital signal processor (DSP) 158, andlocal oscillators (LOs) 161. The specific design and implementation ofthe communications subsystem 101 is dependent upon the communicationsnetwork in which the mobile device 20 is intended to operate. Forexample, the mobile device 20 may include a communications subsystem 101designed to operate with the Mobitex™, Data TAC™ or General Packet RadioService (GPRS) mobile data communications networks, and also designed tooperate with any of a variety of voice communications networks, such asAMPS, TDMA, CDMA, PCS, GSM, etc. Other types of data and voice networks,both separate and integrated, may also be utilized with the mobiledevice 20.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 20 may send and receive communicationssignals over the communication network 141. Signals received from thecommunications network 141 by the antenna 154 are routed to the receiver150, which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 158 to perform more complex communications functions,such as demodulation and decoding. In a similar manner, signals to betransmitted to the network 141 are processed (e.g., modulated andencoded) by the DSP 158 and are then provided to the transmitter 152 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 141 (ornetworks) via the antenna 156.

In addition to processing communications signals, the DSP 158 providesfor control of the receiver 150 and the transmitter 152. For example,gains applied to communications signals in the receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 158.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 101and is input to the processing device 180. The received signal is thenfurther processed by the processing device 180 for an output to thedisplay 160, or alternatively to some other auxiliary I/O device 106. Adevice user may also compose data items, such as e-mail messages, usingthe keypad 140 and/or some other auxiliary I/O device 106, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunications network 141 via the communications subsystem 101.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 110, and signals fortransmission are generated by a microphone 112. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 20. In addition, the display 160 mayalso be utilized in voice communications mode, for example to displaythe identity of a calling party, the duration of a voice call, or othervoice call related information.

Any short-range communications subsystem enables communication betweenthe mobile device 20 and other proximate systems or devices, which neednot necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

FIG. 4 shows a clock buffering circuit 200, in accordance with onenon-limiting embodiment, where the most sensitive RF circuits, forexample, a radio transceiver 202 such as a GSM/GPRS chip set areconnected first to a clock 204 such as a crystal oscillator output withproper impedance matching. A first buffer circuit 206 has an inputconnected to the clock or oscillator output. The output of the firstbuffer circuit 206 is connected to a less sensitive RF circuit 208, forexample, a Bluetooth chip. This buffer circuit 206 typically couldprovide about 40 to about 80 decibel (dB) reverse isolation from itsoutput to the input. Therefore, any analog or digital noise issignificantly reduced, which might come from either the Bluetooth chipor a second buffer circuit 210. The second buffer circuit 210 is alsoconnected to the output of the first buffer circuit 206 and to a thirdbuffer circuit 212 and provides another 40 to about 80 decibel reverseisolation from its output. The output of the second buffer circuit 210could be connected to another analog or digital circuit 214, forexample, a phase locked loop circuit. The output of the third buffercircuit 212 is connected to the reference clock input of the digitalmicroprocessor 216. By this arrangement, the high level digital noise atthe reference clock input of the microprocessor 216 will be reduced byat least about 80 decibels and will have a minimum to no impact to theRF performance.

FIGS. 5A through 5C are interrelated schematic circuit diagrams showingportions of a radio transceiver 300 with various components, and anexample of a clock buffering circuit as described for isolatingdifferent clock signals. A clock distribution network prevents andeliminates digital noise from the microprocessor 302 shown in FIG. 5Bfrom transferring back to a Bluetooth circuit and further to other RFcircuits.

As illustrated, the output of crystal unit or oscillator 304 extends tothe RF clock input directly. Although the clock 304 can operate atdifferent frequencies, in one non-limiting example, the clock is about26.0 MHz. This clock signal passes to a first buffer input formed by atransistor 306 as an NPN transistor. This is designed as an emitterfollower and its output passes directly to a Bluetooth clock input 308.The output of this first buffer 306 also passes to the input of a secondbuffer 308 as a transistor, for example, a PNP transistor. Its collectoroutput signal passes to the microprocessor. This type of circuitarrangement provides good noise rejection back to sensitive RF circuits.As illustrated, other components besides the microprocessor shown inFIG. 5B include circuit components 320, 322 (FIG. 5C) for RF power andbattery power circuits, and including appropriate capacitor circuit 324.The circuits shown in FIG. 5A also include components 330 with the clockand system terminals and various capacitor circuits 332 and resistorcircuits 334 as illustrated.

It should be understood that the buffering circuits as described can beoperative with many different types of Bluetooth chips. Typically, theBluetooth chip is operative as a Bluetooth module and is operative as awireless technology standard for connecting devices to replace cables.It typically operates in radio frequencies at a 2.5 GHz frequency bandand can transmit short distances of about 10 meters or less. Usually ithas a bandwidth of about one megabyte per second (1 MBPS) withindividual packets of up to 2,745 bits. A class three Bluetooth devicecould have a signal strength up to about 100 milliwatts for a range ofabout 100 meters. Usually three basic components are included in aBluetooth module, including a processor, a baseband link controller thatmanages core Bluetooth processes and a radio that implements the 2.5 GHzair interface. The Bluetooth architecture typically includes anapplication program interface (API) libraries that are software modulesthat connect to host application programs to a Bluetooth communicationsystem. The logical link control and adaptation protocol manages highlevel aspects of each connection, including encryption. It can convertthe format of data between application program interfaces and lowerlevel Bluetooth protocols. The link manager can manage physical detailsfor Bluetooth connections. The baseband is a digital engine of aBluetooth system. The Bluetooth radio converts digital baseband data toan from the 2.4 GHz analog signal typically using Gaussian frequencyshift keying (GFSK) modulation.

FIG. 6 is a block diagram of a single-chip Bluetooth circuit shown at400, for example, a BRF 6100/6150 chip that uses CMOS technology. Asshown in FIG. 6, a receiver/transmitter switch 402 receives signals froman antenna 404. The RF signals are transferred into and out of aBluetooth transceiver 406. The Bluetooth transceiver is operative with amodule subgroup that includes a Bluetooth baseband circuit 410,peripherals 412, ROM 414, a RISC processor 416, RAM 418, and clock andpower management circuits 420. The clock input, CODEC interface and hostinterface are illustrated. This type of module can work directly from abattery ranging from about 2.7 to about 5.4 volts in one non-limitingexample and has improved radio frequency performance.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. A mobile wireless communications device comprising: a housing; acircuit board carried by the housing and including an oscillator havingan output and configured to generate a clock signal, a microprocessor, aradio frequency (RF) transceiver, RF circuitry and an analog or digitalcircuit and each carried by the circuit board and operative with eachother wherein the RF transceiver is more sensitive to the digital noisefrom the microprocessor than the RF circuitry, which is more sensitiveto the digital noise than the analog or digital circuit; and clockbuffer circuitry carried by the circuit board and comprising seriallyconnected first, second and third buffers wherein said RF transceiverand said first buffer are connected to said oscillator output, and saidRF circuitry is connected to the output of the first buffer, the analogor digital circuit is connected to the output of the second buffer, andthe microprocessor is connected to the output of the third buffer andsaid buffers configured to reduce the digital noise at the RFtransceiver and followed in order by the RF circuitry and the analog ordigital circuit.
 2. A mobile wireless communications device according toclaim 1, wherein said RF circuitry comprises a Bluetooth module.
 3. Amobile wireless communications device according to claim 2, wherein saidanalog or digital circuit comprises a phased locked loop circuit.
 4. Amobile wireless communications device according to claim 1, wherein saidRF transceiver comprises a GSM/CPRS (Global System for Mobilecommunications/General Packet Radio Service).
 5. A mobile wirelesscommunications device according to claim 1, wherein each buffer providesabout 40 to about 80 decibels of reverse isolation from its output toits input.
 6. A mobile wireless communications device according to claim1, wherein said plurality of serially connected buffers comprisestransistors connected as emitter followers.
 7. A mobile wirelesscommunications device according to claim 1, wherein said housing isconfigured for handheld operation.
 8. A mobile wireless communicationsdevice according to claim 1, wherein said RF transceiver, RF circuitryand microprocessor are operative as a cellular communications device. 9.A mobile wireless communications device according to claim 1, andfurther comprising an antenna carried by the housing and operative withthe RF transceiver.
 10. A mobile wireless communications devicecomprising: a housing; a circuit board carried by the housing andincluding an oscillator having an output and configured to generate aclock signal, a microprocessor, a radio frequency (RF) transceiver, aBluetooth module and a phase locked loop circuit and each carried by thecircuit board and operative with each other wherein the RF transceiveris more sensitive to the digital noise from the microprocessor than theBluetooth module, which is more sensitive to the digital noise than thephase locked loop circuit; and clock buffer circuitry carried by thecircuit board and comprising serially connected first, second and thirdbuffers wherein the RF transceiver and said first buffer are connectedto said oscillator output, and said Bluetooth module is connected to theoutput of the first buffer, the phase locked loop circuit is connectedto the output of the second buffer, and the microprocessor is connectedto the output of the third buffer and said buffers are configured toreduce the digital noise at the RF transceiver and followed in order bythe Bluetooth module and the phase locked loop circuit; and an antennacarried by the housing and operative with the RF transceiver.
 11. Amobile wireless communications device according to claim 10, whereinsaid RF transceiver comprises a GSM/CPRS (Global System for Mobilecommunications/General Packet Radio Service).
 12. A mobile wirelesscommunications device according to claim 10, wherein each bufferprovides about 40 to about 80 decibels of reverse isolation from itsoutput to its input.
 13. A mobile wireless communications deviceaccording to claim 10, wherein said plurality of serially connectedbuffers comprises transistors connected as emitter followers.
 14. Amobile wireless communications device according to claim 10, whereinsaid housing is configured for handheld operation.
 15. A mobile wirelesscommunications device according to claim 10, wherein said RFtransceiver, Bluetooth module and RF circuitry and microprocessor areoperative as a cellular communications device.
 16. A mobile wirelesscommunications device according to claim 10, wherein said antenna ismounted within a lower portion of said housing.
 17. A method of forminga mobile wireless communications device, which comprises: forming ahousing and a circuit board carried by the housing and including anoscillator having an output and configured to generate a clock signal, amicroprocessor, a radio frequency (RF) transceiver, RF circuitry and ananalog or digital circuit and each carried by the circuit board andoperative with each other wherein the RF transceiver is more sensitiveto the digital noise from the microprocessor than the RF circuitry,which is more sensitive to the digital noise than the analog or digitalcircuit; reducing the digital noise at the RF transceiver, the RFcircuitry and analog or digital circuit by forming clock buffercircuitry comprising serially connected first, second and third buffers;connecting the RF transceiver and the first buffer to the oscillatoroutput; connecting the RF circuitry to the output of the first buffer;connecting the analog or digital circuit to the output of the secondbuffer; and connecting the microprocessor to the output of the thirdbuffer wherein the buffers are configured for reducing the digital noiseat the RF transceiver and followed in order by the RF circuitry and theanalog or digital circuit.
 18. A method according to claim 17, whereineach buffer provides about 40 to about 80 decibels of reverse isolationfrom its output to its input.